"Born in a dusty and turbulent environment, comet ISON spent its early years being jostled and struck by siblings both large and small. Surviving a particularly violent first few million years, ISON retreated to the Oort Cloud, where it maintained a largely reclusive existence for nearly four billion years. But around 3-million B.C., a chance encounter with a passing star coerced ISON into undertaking a pioneering career as a Sungrazer. On September 21, 2012, ISON made itself known to us, and allowed us to catalog the most extraordinary part of its spectacular vocational calling.

"Never one to follow convention, ISON lived a dynamic and unpredictable life, alternating between periods of quiet reflection and violent outburst. However, its toughened exterior belied a complex and delicate inner working that only now we are just beginning to understand. In late 2013, Comet ISON demonstrated not only its true beauty but a surprising turn of speed as it reached its career defining moment in the inner solar system. Tragically, on November 28, 2013, ISON's tenacious ambition outweighed its ability, and our shining green candle in the solar wind began to burn out.

"Survived by approximately several trillion siblings, Comet ISON leaves behind an unprecedented legacy for astronomers, and the eternal gratitude of an enthralled global audience. In ISON's memory, donations are encouraged to your local astronomy club, observatory or charity that supports STEM and science outreach programs for children."

Battams has posted a more technical explanation here. He writes there that "while it is conceivable that small chunks of ISON's nucleus still exist, that possibility looks increasingly unlikely and it is with more than a little sadness that we have to declare the comet lost."

As we posted over the weekend, the initial word after ISON's close fly-by of the sun on Thanksgiving Day was that it likely didn't survive the encounter. Then there was more hopeful talk that it just might have held together. Now, NASA has given up that hope.

"The question remains as to whether the bright spot seen moving away from the sun was simply debris, or whether a small nucleus of the original ball of ice was still there. Regardless, it is likely that it is now only dust."

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

DAVID GREENE, HOST:

Last week, we reported on what many were describing as the comet of the century, in part because of the mysteries that it could uncover about our cosmic neighborhood. Comet ISON passed by the Sun on Thanksgiving Day.

Astrophysicist Karl Battams described it this way.

KARL BATTAMS: It has never been into our solar system before. It's a four and a half-billion-year-old frozen chunk of what our solar system was made of. Comet ISON is also a sun grazing comet. Which means it's on an orbit that's going to take it extremely close to the Sun, and go through the Sun's atmosphere.

RENEE MONTAGNE, HOST:

Battams said he felt optimistic the comet would survive its encounter with the Sun, and there was brief hope over the weekend that it actually did. But yesterday, NASA officially declared the comet lost.

GREENE: Writing for NASA's ISON website, Battams said, quote, "It is conceivable that small chunks of ISON still exists." But he said that was unlikely. And so, Battams wrote a short obituary for the comet.

MONTAGNE: It reads: Tragically, on November 28th, 2013, ISON's tenacious ambition outweighed its ability, and our shining green candle in the solar wind began to burn out.

GREENE: Survived by approximately several trillion siblings, the obituary continues, Comet ISON leaves behind an unprecedented legacy for astronomers, and the eternal gratitude of an enthralled global audience. Comet ISON was 4.5-billion years old. Transcript provided by NPR, Copyright NPR.